Duplicating with color producing reagents



June 4, 1968 R. w. GUNDLACH ET Al- DUPLICATING WITH COLOR PRODUCINGREAGEN'IS 3 Sheets-Sheet 1 Filed April 26, 1963 f FIG. 1

F/GZ

POWER SOURCE 2 POWER SOURCE INVENTOR' ROBERT W. GUNDLACH BY VSEVOLOD S;MIHAJLOV A TTORNE Y June 4, 1968 R, w. GUNDLACH ET AL 3,386,379

DUPLICATING WITH COLOR PRODUCING REAGEN'I'S 5 Sheets-Sheet 2 Filed April26, 1963 INVENTOR ROBERT W. GUNDLACH BY VSEVOLOD S. MIHAJLOV A TTQRNE YJune 4, 1968 R. w. GUNDLACH ET AL 3,386,379

DUPLICATING WITH COLOR PRODUCING REAGENTS Filed April 26, 1963 3Sheets-Shem 3 INVENTOR. F G. 11 ROBERT w. GUNDLACH BY VSEVOLOD s.MIHAJLOV ATTORNEY United States Patent 3,386,379 DUPLICATING WITH COLORPRODUCING REAGENTS Robert W. Gundlach, Victor, and Vsevolod E5.Mihajiov,

Rochester, N.Y., assignors to Xerox Corporation, Rochester, N.Y., acorporation of New York Continuation-impart of application Ser. No.185,048,

Apr. 4, 1962, now iatent No. 3,332,347. This application Apr. 26, 1963,Ser. No. 276,198

3 Claims. (Cl. 101469) This invention relates to duplicating processesand, in particular, to the making of duplicates of an original by theaction of chemical reagents. This application is a continuation-in-partof application Ser. No. 185,048 filed Apr. 4, 1962, now U.S. Patent3,332,347.

The tremendous amount of paper work involved in business and governmentadministration today has produced a great interest in reducing theannoyance, time and expense of producing multiple duplicates of originalcopy by present methods. For example, it has been the common practice inclerical work to produce the desired number of copies using carbonpaper. This not only increases the difficulty in handling but also makesit quite difficult to correct errors since each sheet must be correctedindividually. Many duplicating machines are available for duplicatingprinted and other material by processes such as xerography,photo-copying, thermal and diazo processes. However, each of theseprocesses require apparatus of some substantial complexity and/orexpense. Less expensive duplicating processes such as spirit-duplicatingprocesses and stencil-duplicating processes fall short of the desiredcharacteristics on two points. Operators find that both of these arevery messy so that ink or dye stains usually end up on the hands andclothes, and further that the copies made are very poor in imagesharpness. This loss of sharpness in the case of spirit duplicating isdue to slight bleeding of the dye due to the solvent action on the copypaper. In the case of stencil duplicating, bleeding occurs in thestencil due to the necessary characteristic of the stencil materialrequired to permit passage of ink in the character areas.

Also, it is a common characteristic of the less expensive duplicatingprocesses that they require some form of master or stencil which must bemade up as by typing, handwriting, or in a way similar to that formaking an original and is itself not suitable for use as an originaldocument. The making of such stencils commonly adds all thedisadvantageous effects that are found when using carbon paper in makingduplicate copies. Now in accordance with the present invention, it hasbeen found that by using color reagents and evaporation transfertechniques it is possible to greatly simplify low volume duplicatingprocesses. One typewritten copy can be made using a color reagent andthe color reagent can then be transferred to a duplicating masterquickly, cheaply, and easily without any loss of quality in thetypewritten original. Thus, the original remains available for use as anoriginal copy and originals which are received are readily made intomultiple copies without impairing the original, which in many instancesmust be preserved. In this manner, the use of carbon paper copies isavoided, the use of expensive duplicating equipment is avoided, and highresolution copies can be produced rapidly, cheaply, and neatly. Thus, itis an object of the present invention to define a novel copying process.

It is a further object of the present invention to define a dryvapor-thermographic duplicating process producing copies having highresolution.

It is a further object of the present invention to define means forproducin multiple copies of an original by vapor-thermographictechniques.

ice

It is a further object to define a method of producing a color reactiveduplicating master xerographically.

Further objects and features of the invention will become apparent whilereading the following description in connection with the drawingswherein:

FIG. 1 is a crosssectional view of one embodiment of a typewriter ribboncarrying a color reagent;

FIG. 2 is a face view of a second embodiment of typewriter tape carryinga color reagent;

FIG. 3 is a diagrammatic illustration of simplified apparatus forcarrying out one step of the inventive process;

FIG. 4 is a diagrammatic illustration of the simplified apparatus shownin FIG. 3 particularly illustrating a second step in the process;

FIGS. 5 and 6 are diagrammatic illustrations of rotary apparatus forcarrying out the process steps shown in FIGS. 3 and 4, respectively;

FIG. 7 is a diagrammatic illustration illustrating exposure of axerographic plate to an original;

FIG. 8 is a diagrammatic illustration of development of the xerographicplate using a color reactive developer;

FIG. 9 is a diagrammatic illustration of thermographic duplicating usingthe plate developed as in FIG. 8;

FIG. 10 is a diagrammatic illustration of duplicating apparatus inaccordance with the invention;

FIG. 11 is a diagrammatic illustration of another embodiment ofduplicating apparatus in accordance with the invention.

For simplicity of illustration, the invention will first be describedusing a typewriter to produce the original. As will be set forth below,however, this is only by way of example and the invention comprehendsvarious other modes of producing the original.

In producing a typewritten original in accordance with the instantinvention, the usual typewriter ribbon for a typewriter is replaced witha similar ribbon which has been inked with a conventional typewriter inkand also with a color reagent. This color reagent, which is hereintermed Chemical A, may be one of a number of chemicals for which areaction partner exists so that when the two are combined, an intenselycolored substance is formed. The reaction partner is herein termedChemical B. Following is a partial listing of suitable materials forChemical A with corresponding reaction partners, Chemical B:

Chemical A Pyrocatcchol. Aniline.

Dithiooxamide. N-dimethyl-dithiooxamide.

N ,N -bis(2-hydroethyl) dithiooxamide.N,N-bis(carbcry-methyl)dithiooxamide. Other dithiooxamide derivatives.Hydrazine.

Pyrogallol. N-(p-liydroxyphcnybglycinc. Hydroxylamine.

Diaininophenol hydrochloride. p-Methylaminophenol sulfate.l)ichlorohydroquinone.

Thiourea.

Chlorohydroquiuonc. Bromohydroquinone.

Gallic acid.

Other organic reducing substances. Ammonia salts.

Ammonium bcnzoate. Ammonium acetate.

Ammonium carbonate.

Chemical B (1) Iron salts. (2) Vanadium salts.

(3) Copper salts.

Nichel salts. Cobalt salts.

(4) Silver salts.

(5) Organic diazonium salts and similar.

Potassium dichrom ate.

As will be further described below, material typed using the ribboncontaining Chemical A may be used to form a mirror-image master fromwhich, in turn, multiple direct-reading copies may be produced on papertreated with the corresponding Chemical B.

FIGS. 1 and 2 show various embodiments of typewriter ribbon inaccordance with the invention. In FIG. 1, the typewriter ribboncomprises support tape 11 carrying composition 12 of ink and anappropriate Chemical A. Support tape 11 can be any material suitable foruse as a typewriter ribbon such as cloth fabric, metal foil, paper orplastic. Because non-uniformities are emphasized in a duplicatingprocess, the support tape is preferably of a material that facilitatesuniform typing. As is well known in the typewriter industry, greateruniformity is commonly achieved by using a non-reuseable ribbon. Suchribbons are conventionally referred to as carbon ribbons and use a thinplastic support tape. In a preferred embodiment, typewriter ribbon foruse in accordance with the resent invention comprises a polyethylenefilm coated with typewriter ink and Chemical A in which Chemical A isabout -50% by weight of the ink and Chemical A mixture. Spray coating,roll coating, dip coating, evaporation coating, or other conventionalcoating means may be used. Alternatively, a cloth ribbon is saturatedwith an ink and Chemical A, of the same nature as for the plasticribbon, by running the ribbon through a bath of the solution or by somesimilar process. For example, a silk typewriter ribbon dipped in amixture of grams rubcanic acid to 100 grams of black typewriter ink.

FIG. 2 shows an embodiment of a typewriter ribbon 14 in accordance withthe invention in which one half of the ribbon 15 is coated or permeatedwith the ink and color reagent solution as in FIG. 1 and the other halfof the ribbon 16 is coated with a chalk-like material for correctingerrors. The correcting materials are selected for their ability toconceal a typed letter when the same letter is typed over with theerror-correcting half of the ribbon, and further for their ability toform a vapor barrier so that no vapor can issue from the erroneouslytyped letter. For example, titanium dioxide or zinc oxide in a waxbinder or the like have been found suitable for coating the correctionhalf of the ribbon. Using a ribbon of the type illustrated in FIG. 2 andtyping only a single copy increases ease of typing tremendously sincethe typist does not have to worry about material on carbon copies and,in correcting an error, does not have to use anything outside of thetypewriter, itself, such as erasers or other materials available forcorrecting typewritten material. The typist merely backspaces, pushesthe ribbon-position lever and retypes the letter in order to obliterateit. Thus, the typists hands are not required to leave the keyboard ofthe machine in correcting errors.

In accordance with the invention, a single sheet of original typed copyis made using a ribbon in the typewriter corresponding to one of theembodiments illusu trated in FIGS. 1 and 2. It is desirable that thetyping be highly uniform in order to obtain good copies. Since theaverage typist does not have good uniformity of touch, an electrictypewriter has been found preferable.

FIG. 3 shows a simple manually operated embodiment of apparatus toproduce multiple copies of the typed original. This apparatus comprisesheat conductive pad 18 such as will maintain a uniform low ambienttemperature on its surface when a heated roller is rolled across a sheetof material resting on such surface. Thus, the heat conductive pad maybe a metal such as aluminum having enough mass to absorb a considerableamount of heat without changing its over-all temperature by asignificant amount. This pad should have a surface area adequate tosupport the largest size of copy sheet that may be desired. Arectangular size of about 10 x 15 inches is adequate for most purposes.The pad should preferably be not less than one quarter inch thick, butthis is not limiting since the heat absorption and dissipationcharacteristics are controlling.

In accordance with the inventive process, master sheet 19 is positionedin contact with the surface of the heat conductive pad. This mastersheet may be made of substantially any material that has a smoothfinished surface such as a majority of plastic materials, metal foils,glass or paper. By way of example, a 1 mil thick sheet of celluloseacetate has been used. Nonporous materials have generally yielded thebest results but whether this is due to thermal characteristics,absorption characteristics, or some other characteristics is not fullyunderstood at this time. Thickness of the master sheet is not criticaland success has been obtained with sheets of 1 mil and of 15 milsthickness. The determining criteria relevant to this last characteristicare the amount of heat available and the permissible time for vaporizingvolatile material from the surface of the master sheet. An excessivethickness will either act as a heat insulator or will dissipate the heattoo rapidly for eflicient operation. It is preferably less than about 10mils thick so that it will not absorb or hold an excessive amount ofheat. However, it can be much thicker than 10 mils; for example, a inchthickness of window glass has been found suitable.

Typed original 20 is next placed face down against the smooth surface ofthe master sheet and heated roller 22 or other heat applicator such as aheat plate or heat lamp is used to apply heat against the back of typedoriginal 20. Heat applicator 22, as illustrated, is a metal rollercontaining thermal element 23 which is connected through handle 24 ofthe roller to power source 25. In rolling the roller against the back ofthe typed original or in applying heat in one of the other wayssuggested, the intensity of the heat and the length of time must be suchas to cause a portion of Chemical A in the characters of the typedoriginal to sublime or otherwise change to a vapor. Suitable heat may beapplied by operating the roller at a temperature of about 200 to 400 F.and by rolling the heated roller across the back surface of original 20at a speed of about /2 to 4 inches per second. With the roller at 240 aspeed of about 1 inch per second has been used. These ranges have beenfound suitable using rubeanic acid as Chemical A. While still highertemperatures produce good results at faster speeds, such temperaturesincrease the likelihood of heat damage to the materials or equipment.Safeguards against such damage can be built in, but would increaseexpense. In the apparatus of FIG. 4, heat conductive pad 18 maintainsmaster sheet 19 at a temperature relatively lower than that attained bytyped original 20 when the heat is applied to it. Thus, a portion of thecolor reagent Chemical A is a transferred by vaporization andcondensation from the typed original to the master sheet. Since thematerial thus transferred is transferred between surfaces that are invirtual contact, there is no significant loss of resolution. Since theamount of liquid transferred is very minute, bleeding effects are practically nonexistent.

After the color reagent, Chemical A, has been thermographicallytransferred to master sheet 19 as described above in connection withFIG. 3, the master sheet is removed from pad 18. Then as illustrated inFIG. 4, copy sheet 27 treated with Chemical B is positioned on pad 18with its treated surface facing -away from the pad. Copy sheet 27 maycomprise any ordinary paper which has been chemically treated inaccordance with the invention. Preferably, the paper is smooth surfacedto permit a more uniform contact in the duplicating process. If thecolor reagent, Chemical A, is dithiooxamide, otherwise known as rubcanicacid, the copy paper is appropriately treated with a coating solutionof, for example, nickel salts dissolved in water, alcohol or similarsolvent to a solution of 5% to 25% by weight volume. For imtion of 25%weight by volume of copper sulfate in water has also produced effectiveresults. The solution may then be coated on the paper by spraying,dipping, flowing, rolling, wiping or similar process. Some moisturecontent in the copy paper has been found to increase density further.Thus casein coated papers or paper treated with a humectant such as asorbitol or glycerine have been found advantageous.

With the treated paper lying face up on the pad, master sheet 19 ispositioned in face-to-face contact with the copy sheet so that theimage-carrying surface of the master sheet is in con-tact with thetreated surface of the copy sheet. Now, when heated roller 22 or similarheat applicator applies heat to the free surface of the master sheet, aportion of the color reagent, Chemical A, in character configuration onthe master sheet is transferred by evaporation and condensation to thesurface of the copy sheet. Where Chemical A contacts the copy sheet, itreacts with its reaction partner, Chemical B, on the copy sheet toproduce a visible image.

Since transfers by the process described above are always byface-to-face contact in the embodiments described above and since thecolored product is insoluble preventing bleeding, a very high resolutionis obtainable in the copy.

In a further embodiment of the invention, it is possible to eliminatemaster sheet 19 described in FIGS. 3 and 4, but with a slight loss inresolution. In this further embodiment, treated copy sheet 27 is placedwith its treated surface adjacent to the surface of pad 18. Then typedoriginal 20 carrying Chemical A in its typed characters, is positionedwith its typed surface adjacent to the untreated surface of copy sheet27. When heat is applied as by roller 22 or other heat applicatingmeans, Chemical A vaporizes and condenses on copy sheet 27. If copysheet 27 is made of a very porous paper or paper-like material, some ofthe vapor will pass through the pores reaching the treated surface ofthe copy paper. Otherwise, Chemical A should be chosen as a materialthat does not sublime but passes through a liquid phase. When thismaterial condenses as a liquid on the untreated surface of the copysheet, it is absorbed by the copy sheet and passes through in order toreact with the reaction partner, Chemical B, on the opposite surface ofthe copy paper. As is apparent, in order to maintain an acceptable levelof resolution, the copy paper in accordance with this embodiment shouldpreferably be quite thin-in the nature of 21 mil or less. However,thicker copy papers may be used with the attendant disadvantage ofslightly lower resolution. A second method for going directly fromoriginal to copy requires the use of substantially transparent copysheets. The transparent copy sheet carrying Chemical B is positionedwith its coated surface facing the typed surface of the original. Thetwo are heated causing vaporization and chemical reaction on the contactsurface of the copy sheet. The image is then directly readable throughthe reverse side of the copy sheet.

FIGS. 5 and 6 show an embodiment of simple rotary apparatus forperforming the process illustrated in connection with FIGS. 3 and 4. Inthis embodiment, cylinder 31 and cylinder 32 perform the functions ofpad 18 and roller 22, respectively, of FIG. 3. It is consideredpreferable that one of the cylinders have a slightly yieldable coatingand high friction qualities. For example, covering one cylinder with asurface layer of silicone rubber has been found advantageous. Thus,cylinder 32 is a heated cylinder. In this embodiment, the thermalcharacteristics of cylinder 31 are not particularly critical. However,it has been found that cylinder 31, because of its close proximity inoperation to cylinder 32, is ihclined to draw heat from cylinder 32reducing its temperture and causing non-uniform heat distribution. Thus,it is preferable to heat cylinder 31 as well as cylinder 32 asillustreated by thermal elements 23, or to cover cylinder 31 with a heatinsulating layer so as to reduce heat dissipation. Good results havealso been obtained by heating only cylinder 32, but maintaining the twocyiinders in continuous rotating contact for an extended period prior touse so as to reach a point of temperature stability, With thetemperature on heated cylinder 32 stabilized in the range between 200and 400 F., master sheet 19 and typed original 29 are run in betweencylinders 31 and 32 and advanced by rotation of the cylinders. Motor 33is illustreated as driving cylinder 31 through drive means 34. However,it should be understood that the same operation can be performed by amanual crank. As the two sheets run between the two cylinders, heat fromheated cylinder 32 penetrates to the characters in the typed originaland causes the color-reagent Chemical A to vaporize into the minutespace between the two sheets. It is pointed out that this minute spaceis the natural result of positioning two smooth sheets in contact. Amere positioning of two sheets in contact in this manner even when theyare run between pressure rollers will not eliminate all space betweenthe contacting surface. Minor variations always present in such surfacesprevent complete elimination of such space. As the two sheets passbetween the two cylinders, some Chemical A is transferred to the mastersheet. The image on the master sheet is commonly a weakly visible image.

While not necessarily limiting as to how the transfer of Chemical Aactually takes place, it is theorized that it vaporizes due to the heatbetween the two sheets and then as the two sheets issue from between thecylinders, they are cooled by the ambient temperature of the air so thatcondensation or sublimation of Chemical A occurs in part on bothsurfaces. It has been found that transfers of Chemical A to the mastersheet have consistently attained levels of 75% or more transfer. Whilethe reason for this is not completely understood, it is possibly due tothe use of master materials which are relatively more heat conductivethan the paper ,used for the original. This would allow the master tocool faster and thus condense the evaporated chemical at a higher ratethan the original. It should be noted that in this embodiment there isno requirement as to Whether the master sheet or the typed original isin direct contact with the heated cylinder. It is only necessary thatenough heat be applied to one or the other so that heat penetrates thesandwich and volatilizes some of the color reagent.

Next, as illustrated in FIG. 6, a treated copy sheet is positioned withits treated surface in contact with the surface of the master sheet nowcarrying transferred Chemical A in the mirror image configuration of theoriginal. The two sheets are advanced as a sandwich between cylinders 31and 32 in a second vaporthermographic transfer process similar to thatillustrated in FIG. 4. Again the heat may be applied to either surfaceof the sandwich so long as it is adequate to cause vaporization of someof the Chemical A present on the master sheet. As the two sheets passbetween the cylinders, Chemical A is transferred to the copy sheet.While the apparatus of FIGS.

5 and 6 is capable of considerably more automation than that of thehighly simplified apparatus illustrated in FIG. 3, it still requires alarge extent of manual operation.

While the illustrated embodiments of FIGS. 1-6 have been describedgenerally in relation to the reproduction of type-written material, theinvention is in no way limited to typewritten material. Handwrittenmaterial using a pen or machine drawn material using some form of stylusdevice, in which the pen or stylus uses a drawing solution containingcolor reagent Chemical A, is suitable as an original for reproduction inaccordance with the inventive process. A useable original may also beproduced by xerography from an original that does not contain a volatilecolor reagent. Such a xerographic copy for use as an original in theinventive process would be made using Chemical A in a developer materialfor the xerographic image. It has been found for example that rubeanicacid, itself, will act as a suitable toner in developing anelectrostatic latent image in the xerographic process. Thus,

7 FIGS. 7-11 illustrate embodiments of the invention in which theduplicating master containing Chemical A has been formedxerographically.

FIGS. 7-9 are greatly simplified illustrations roughly comparable toFIGS. 1-4 but using a xerographic process rather than a typewriter forforming the duplicating master. FIG. 7 illustrates exposure ofxerographic plate 40 to a light pattern from original 41 using lightsource 42 and lens 43. While greatly simplified for illustrativepurposes, this figure is meant to represent conventional formation of axerographic latent electrostatic image in which a xerographic plate iselectrostatically charged in the dark and then selectively discharged bya light pattern.

Plate 40 carrying the latent electrostatic image formed in FIG. 7 isthen developed by a developing device 45 as illustrated in FIG. 8. Thedeveloping device illustrated in FIG. 8 represents a device known to theart as a magnetic brush. As illustrated, this comprises a magnet element46 enclosed in a non-magnetic envelope 47. The brush 48 is formed offerromagnetic particles which form brush-like bristles under theinfluence of the magnet. For xerographic development, a pigmenteddeveloping toner is mixed in with the ferromagnetic particles beforeformation of the brush. The mixture is known as a toner-carrierdeveloper in which the relatively large ferromagnetic particles carrythe smaller toner particles by virtue of triboelectric attraction. It isnecessary that the toner material be widely separated in thetriboelectric series from the ferromagnetic particles in order to obtaintriboelectric attraction and charging between the toner particles andthe ferromagnetic particles. It has been found that rubeanic aciditself, in its common commercial powder form, is suitable withconventional magnetic brush carrier particles such as described in US.Patent 3,015,305. Conventional resin toner can be added along with theru'beanic acid to enable fusing of the image. Rubeanic acid toner canalso be produced by the same technique as conventional Xerographictoners, substituting the rubeanic acid for the carbon black or otherpigment. Where a good visible xerographic image is desired, bothconventional pigment and rubeanic acid may be added together. Resinmaterial in the toner helps control the evaporation of the rubeanic acidin the duplicating process permitting greater uniformity over a largernumber of copies and has also been found to reduce ghosting. While FIG.8 illustrates magnetic brush development, other forms of xerographicdevelopment such as cascade and powder cloud development are equallyoperable.

The developed image on the xerographic plate can be used in a directthermographic transfer to a metal salt treated copy sheet 27 asillustrated in FIG. 9. Treated copy sheet 27 is positioned on top of theduplicating master and heated roller 22 is passed over the back of copysheet 27 so that heat from the roller passes through sheet 27 and heatsthe image material on the surface of the xerographic plate causing someof Chemical A to evaporate and react with Chemical B on the copy sheet27. As illustrated in FIGS. 7-9, a mirror reverse image would be formedon the xerographic plate so that a vapor thermographic transfer directlyto a treated copy sheet, produces a direct reading image. However, topreserve the xerographic plate, it may be desirable to form a directreading image on the xerographic plate by the addition of a mirror inthe exposure system of FIG. 7 and then after development, transferringthe image containing Chemical A in a conventional xerographic transferprocess to an intermediate duplicating sheet or web which in turn is runagainst the treated copy paper for multiple duplication. The addition ofa mirror permits forming a direct reading copy on the xerographic plateso that upon transfer to an intermediate master, a mirror image isobtained on the master suitable for making direct reading copies on thetreated copy paper.

Complete system apparatus using a mirror and an intermediate master isillustrated in FIG. 10. FIG. illustrates apparatus suitable forperforming all of the operations from the original through to themultiple copies on metal salt treated paper. Xerographic drum 50 iselectrostatically charged by charging device 51 and exposed to a lightpattern of original 41 by means of lens 43, mirror 52 and projectionslit 53. Original 41 and drum 50 are moved synchronously in accordancewith slit projection techniques by motor 55. After exposure, xerographicdrum is developed with developer material containing Chemical A in adeveloping system depicted as cascade development means 56. Thedeveloped image is transferred to intermediate duplicating drum 57 underthe infiuence of a transfer potential applied to drum 57 by means ofvoltage source 58. While not necessary for Operability of the system,image fusing means 60', depicted as a vapor fusing chamber can be usedfor liquifying and fusing resin that may be mixed with Chemical A in thedeveloper. Vapor fusing, in accordance with this invention, has theadvantage in that it does not vaporize or evaporate Chemical A as wouldheat fusing. As set forth above, the use of some amount of resin toneralong with fusing improves the uniformity of reproduced copy but hassome disadvantage in the present embodiment in making it more difficultto clean the intermediate master for reuse. Where resin and fusing isused, the intermediate master is preferably coated with a relativelynonporous material such as polytetrafluoroethylene or polyethyleneterephthalate. During transfer of the image from xerographic drum 59 tointermediate master 57, intermediate master 57 is supported firmlyagainst drum 50 as by cam 61 positioned as illustrated. After transferof the image to intermediate master 57, cam 61 is rotated to separatethe xerographic drum from the intermediate master. Treated copy sheets27 are then fed by a feed dog 62 between the intermediate master 57 anda heated roller 63 producing multiple copies of the original. With thexerographic drum separated from the intermediate master duringduplicating, the final run-off can be operated at a higher speedindependently of speed limitations in the formation and transfer of thexerographic image. After the desired number of copies have been run off,cleaning web 65 is brought into position against the intermediate masterby means of pivot roller 66 in order to clean residual image materialfrom the intermediate master. The cleaning web 65, such as described inUS. Patent application S.N. 77,922 filed Dec. 23, 1960, is operated by amotor 67 and is preferably run in a reverse direction from the rotationof the master for optimum cleaning. Before forming a new xerographicimage, drum 50 is cleaned by cleaning brush 68.

While involving expense in consumable materials, some simplification canbe derived from using the same material both as the xerographic plateand as the duplicating master. Preferably, such a material is of thenonreuseable variety which may be discarded after use. For this purpose,a xerographic grade of zinc oxide in an insulating resin binder coatedon paper is conventional and available commercially. A particularadvantage in a system using zinc oxide binder paper is that cleaning isunnecessary and ghosting problems are greatly reduced. An embodiment ofapparatus suitable for utilizing a nonreuseable xerographic sensitivematerial is illustrated in FIG. 11. By Way of example, the original tobe reproduced is depicted as reel of microfilm 70 from which a lightpattern is projected by means of light source 71, lens 72 and exposureslit 73 to form a latent electrostatic image on xerographic web 75 whichis suitably a zinc oxide binder paper. Web 75 is fed from supply reel 76through charging device 77 past exposure slit 73 to magnetic brushdeveloping device 78. Magnetic brush developing device 78 carrying amagnetic brush of ferromagnetic carrier particles, resin and Chemical A,is rotated in a direction reverse to the web movement by a motor 80against web 75 and then carries the brush ma terial along the surface ofnonmagnetic shield 81 until the ferromagnetic particles fall out of theinfluence of magnetic elements 82 so that the brush is disrupted and thedeveloping material falls back into the developer compartment 83 fromwhich a new brush is formed. Web 75 supported on rollers 84, is carriedafter development into vapor fusing chamber 85 where the Chemical A andresin material is fused to enable greater uniformity in the followingduplicating steps. Web 75 leaves fusing means 85 to pass through aselectable number of copying stations. Each copying station comprises afeed roll 86 for metal salt treated paper 87 and heated roller 88 forpressing paper 87 against web 75 while applying heat. Back up rollers 90are provided at each duplicating station. Solenoid actuated positioners91 are connected to each of heated rollers 88 to enable selectableoperation of each of the duplicating stations. For example, if only oneduplicate copy is desired, the solenoid 91 will be actuated in eachduplicating station except one in order to retract the heated rollerspreventing operation of the duplicating stations. After passing throughthe duplicating stations, web 75 is Wound up on take up reel 92.Movement of web 75 and movement of the original to be reproduced areoperated synchronously by means of motor 93. The web 75, after beingwound up on take up reel 92, can be reused at a later time for runningoff further copies. For example, a sheet representing a particular pageof copy may be cut off the reel of used web and mailed with or withoutduplicating copies so that further copies may be run off from it at adistant location.

In the disclosed embodiments, the source of heat while generallydescribed as a heated roller or cylinder is not limited to such but canbe any source of heat capable of supplying the necessary heat to causevaporization of Chemical A. Thus, photoflash lamps, infrared lamps, anysource of intense radiant illumination, sources for supplying hot air byblowers or convection currents and various electrical heating means areall contemplated as useable with the present inventive process. Variousavailable machines may also be used such as the thermal processingmachinw available under the trade name, Thermo-Fax, available fromMinnesota Mining and Manufacturing Company of St. Paul, Minn., and thethermal processing machines available under the trade name Kalfax,available from the Kalvar Corporation of New Orleans, La.

While the present invention has been described as carried out inspecific embodiments thereof, there is no desire to be limited thereby,but it is intended to cover the invention broadly Within the spirit andscope of the appended claims.

What is claimed is:

1. A method of image duplicating from a xerographic master whichcomprises forming an electrostatic latent image on the surface of axerographic plate, developing said latent image with a toner compositioncomprising a thermoplastic material and a vaporizable color producingreagent, contact in the presence of heat said developed image with thesurface of a salt treated copy paper such that a portion of said colorproducing reagent vaporizes and reacts with the salt component of saidcopy paper to produce a visible image.

2. The process as described in claim 1 wherein said color producingreagent is a dithiooxamide derivative and said salt is a metal salt.

3. The process as described in claim 2 wherein said dithiooxamidederivative is rubeanic acid and said metal salt is at leats one sulphateselected from the group consisting of sulphates of nickel, copper andcobalt.

References Cited UNITED STATES PATENTS 2,582,932 1/ 1952 Lustbader101-149.4 3,122,093 2/1964 Lynch et a1. 101149.4 2,889,758 6/1959 Bolton95-1.7 3,115,814 12/1963 Kaprelian 951.7 2,297,691 10/1942 Carlson101-149 X 2,936,707 5/1960 Maguire et a1. 101426 3,054,692 9/1962 Newmanet a1. 101-426 3,094,417 6/ 1963 Workman.

3,280,735 10/1966 Clark et al. 10l-149.4

DAVID KLEIN, Primary Examiner.

1. A METHOD OF IMAGE DUPLICATING FROM A XEROGRAPHIC MASTER WHICHCOMPRISES FORMING AN ELECTROSTATIC LATENT IMAGE ON THE SURFACE OF AXEROGRAPHIC PLATE, DEVELOPING SAID LATENT IMAGE WITH A TONER COMPOSITIONCOMPRISING A THERMOPLASTIC MATERIAL AND A VAPORIZABLE COLOR PRODUCINGREAGENT, CONTACT IN THE PRESENCE OF HEAT SAID DEVELOPED IMAGE WITH THESURFACE OF A SALT TREATED COPY PAPER SUCH THAT A PORTION OF SAID COLORPRODUCING REAGENT VAPORIZES AND REACTS WITH THE SALT COMPONENT OF SAIDCOPY PAPER TO PRODUCE A VISIBLE IMAGE.